Treatment of wood separators



" 2p proportions and Patented Jan. 18, 1927.-

UNITED STATES cmrnunc. canrnn'rna, or NIAGARA FA ILLS, NEW YORK, ASSIGNOR TO U. S1 LIGHT & HEAT CORPORATION, OF NIAGARA FALLS, NEW YORK, A CORPORATION OF NEW YORK.

Ho Drawing. Application filed June 21,

This invention relates to the treatment of wood separators for storage batteries. An object of the invention is to so treat a wood separator'as to get the fibres of the 5 wood in proper colloidal condition so as to more readily absorb and transfer sulphuric acid and so as to more readily difi'use bat ter acid. s

further object is to so prepare the sepa- 1o rator that it will not be readily attacked by battery Lelectrolyte, thereby increasing the separator life.

When the wood of the separator is in proper colloidal condition it has the prop- .lp erty of absorbing acid of greater density than that of the electrolyte surrounding it. This .increases the conductivity of the separater."

In the process as outlined below, exact riods of time have been given as representing the best practice so far determined, but it is notiintended that the stated-proportions and time periods shall be construed as otherwise than illustrating the principles of the process, it being understood that variations in proportions and details of treatment may be resorted to withoutdeparting from the principles of the invention as defined in the appended claims. 9 In the specific process described, Port Orford cedar has been selected as a wood to be 3 treated, as this has been found specially adapted for use as aseparatorr The process is, however, equally adapted for'use with 85 other woods.

In carrying out the process, dry separators cut to proper size, are placed together, pulping pre erably on edge, in a tank,-covere with water and boiled for a period of approxi- 4omately one hour. The separators are then placed in a solution of caustic soda which should be of-a strength of 18% solution or over, say of 1.275 specific gravity, in which the separators remain for a period of one, hour or more. Separators are then removed from this solution and .acidulated with sul= 'phuric acid and thorou hly washed in water. The are then rea y for service.

It has con found that separators treated in this manner are characterized by an excessive shrinkage of the wood fibre in the direction of the fibre length and remain practically unchanged in the other direction of thewooil. ThlS is to be distinguished'from 5 treatments which have been proposd heretornaurnanr or wo on SEPARATORS.

199a. Serial-No; 646,987.

fore, using a low concentration of caustic in which the separator is characterized by a swelling ofthe fibres'in the direction of their diameter, while remaining practically unchanged in length. This difi'erence in characteristics is apparently due to the fact that the high concentration of caustic will not attack the lignocellulose. It has also been found that this high concentration of canstic does not! break upthe lignocellulose constituents and therefore does not free certain deleterious substances which are freed by treatment with weaker caustic solution. The acidulation step is desirable as assisting to prevent attack and breaking up of the lignocellulose, for it is obvious that if the separator were treated with a strong caust c,w1thout subsequent acidulation, the caustic would be diluted in the washing step,

passing through the lower concentration, therefore attacking the lignocellulose and freeing the deleterious substances. I This theory is substantiated by the observation that in the treatment with the concentrated causic there is ractically no discoloration of the treating liquid, whereas. by treatment with the di ute caustic, the treating liquid is verymuch discolored.

The initial treatment with water is to produce an i itial swelling of the fibres.

What I claim as new and desire to secure by. Letters Patent of the United States is 1. The process of treating wood for use as battery separators which the wood with a concent caustic solution and controlling the. process to prevent the wood.

.2. T e process in battery separators which comprises treating the wood with concentrated caustic solution and controlling the process to preventpul ing the wood, then acidulating and was ing out the treating solution.

3. The process of preparing wood foruse in battery separators which comprises treating the wood with a solution of caustic of not less than 18% concentration and cona trolling the process to prevent pulping the wood, thereafter acidulating and washing out the treating solution.

4. The process of preparing wood for use in battery separators which consists in treating the wood with a solution 'of caustic of not less than 18% strength and controllin the process to prevent pulping the wood comtprises treating rate of preparing wood for use lilo? in battery separators which comprises boiling the wood in water, thereafter treating with caustic solution of approximately 1.275 specific gravity, thereafter acidulating, and

thereafter washingin water.

6. A battery separator comprising wood treated with concentrated caustic solution, in

characterized by the fact that the wood fibres have been excessively shrunk in a direction of length without appreciable change in fibre dimensions in other directions.

In witness whereof, I have hereunto sub- 1 scribed my name.

CAMPBELL C. CARPENTER. 

